1. Field of the Invention
The present invention relates to a flame-retardant polypropylene resin composition having polypropylene resin as a main component, and more particularly, to a polypropylene resin composition which includes a polypropylene resin with a melt flow rate of 4-18 g/10 minutes, a halogen-containing flame retardant additive with a low melting point, an antimony oxide, an ultraviolet stabilizer, a silane coupling agent, and titanium dioxide used as a light-blocking agent. The resin composition exhibits good weathering properties and maintains the same level of flame retardancy as well as other physical/mechanical property characteristics after a hydrothermal dipping treatment.
2. Description of the Related Art
Polypropylene resins are used extensively in home electronic appliances, building members, interior decorating materials, and automobile parts due to their excellent processing characteristics, chemical resistance, and mechanical strength. These resins, however, lack flame retardancy and are therefore difficult to use in the manufacture of automobile parts or electronic components which require protection against the danger of fire. As a result, the effects of the addition of various organic, inorganic, and phosphorus flame retardant additives on flame retardancy in polyolefin resins have been studied extensively.
Japanese Patent Publication Nos. 53-92855, 54-29350, 54-77658, 56-26954, 57-87462, and 60-110738 disclose preparation methods of producing flame retardant polypropylene resin compositions by adding inorganic flame retardant additives such as magnesium hydroxide, aluminum hydroxide, or hydrotalcite. However, in order to obtain a flame retardant grade of V-0, a resin composition including more than 50% by weight of the inorganic filler is needed. This high level of inorganic filler results in a deterioration of the processability of the resin, generation of gas during processing, and a decrease in impact strength of the resin product.
Japanese Patent Publication No. 53-30739 discloses flame retardant polypropylene resin compositions produced by adding organic halogen-containing flame retardant additives such as decabromodiphenylether and dodecachloro-dodecahydromethanodibenzocyclooctane. Other flame retardant polypropylene resin compositions are produced by adding tetrabromobisphenol A bis-(dibromopropylether), bis-(tribromophenoxyethyl)tetrabromobisphenol A ether, hexabromo cyclododecane, and tetrabromobisphenol A. Although these resin compositions exhibit excellent flame retardancy and processability, weatherability and resistance to hot water are poor making it difficult to use the resin in outdoor products such as light bulb sockets for Christmas tree lights.